The present invention relates to a system and method of measuring characteristics of an engine, and more particularly to an engine testing system (so-called engine bench system) for measuring various characteristics of an engine by directly connecting the engine with a dynamometer functioning as a driving power absorber and to a method of measuring the engine characteristics.
Generally, an engine testing system is constructed by connecting a dynamometer with a combination of an engine and a transmission. The control of the engine is executed by controlling a throttle opening of the engine, and the control of the dynamometer is executed by controlling a speed and a torque on the basis of detection signals detected by a speed detector and a torque detector provided in the dynamometer. This control is executed by PID control (Proportional, Integral and Derivative Control) using a controller.
However, such an engine testing system using the PID control has a possibility that the shaft connecting the dynamometer and the engine may cause resonance vibration due to a pulsation torque generated by the engine. Therefore, it is necessary to execute the PID control of the dynamometer within an engine operation range where a frequency of a pulsation vibration generated by the engine is smaller than a resonance frequency of a mechanical system of the dynamometer, the shaft, and the engine. Therefore, it is difficult to execute a high-responsibility speed control under this limitation due to the resonance frequency of the mechanical system.
Although it is possible to construct the mechanical system using a high rigidity shaft so that the resonance frequency of the mechanical system becomes out of an operation range of the engine, a speed control using the PID control has a limitation that uncertain factors such as an engine pulsation torque affects the control response of the speed control.
It is therefore an object of the present invention to provide a system and method which is capable of stably measuring engine characteristics in high speed by constructing a speed control system of the system via the structured-singular-value synthesis method.
An aspect of the present invention resides in a system for measuring characteristics of an engine. The system is constructed by connecting the engine with a dynamometer functioning as a driving force receiving member by means of a shaft. The system comprises a speed control system which controls at least one of an engine speed and a dynamo speed. The speed control system comprises a first block represented by a mechanical transfer function, a second block represented by an electric transfer function, and a speed controller. The first block receives an engine torque and a dynamo torque and outputs the engine speed, an axial torque and the dynamo speed. The second block receives a command dynamo torque and outputs the dynamo torque. The speed controller receives one of a command engine speed and a command dynamo speed, and at least one of the engine speed and the dynamo speed, and outputs the command dynamo torque. The speed controller is represented by a transfer function designed using the structured singular value synthesis method so as to be adapted to the mechanical transfer function and the electric transfer function.
Another aspect of the present invention resides in a method for measuring characteristics of an engine using a speed control system for controlling at least one of an engine speed and a dynamo speed in a system of the engine, the dynamometer, and the shaft. The method comprises the steps of: receiving an engine torque and a dynamo torque and outputting the engine speed, an axial torque and the dynamo speed in response to the engine torque and the dynamo torque; receiving a command dynamo torque and outputting the dynamo torque in response to the command dynamo toque; and receiving one of a command engine speed and a command dynamo speed, and at least one of the engine speed and the dynamo speed, and outputting the command dynamo torque in response to the received signals by means of a speed controller which is represented by a transfer function designed using the structured singular value synthesis method so as to be adapted to the mechanical transfer function and the electric transfer function.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.